Add a way to uninstall somehow

[necessarily-equal]

This doesn't need to be part of the updater, but we should provide a way to uninstall the game somehow.

[DolceTriade]

I did have this bookmarked forever in my thing. We should probably do this: https://nsis.sourceforge.io/Add_uninstall_information_to_Add/Remove_Programs

[DolceTriade]

maybe add an -uninstall flag to the updater too.

[illwieckz]

And an uninstall button in the advanced window.